A common problem with liquid heating and cooling systems, and liquid distribution systems in general, is the accumulation of gas pockets in distribution pipes. Dissolved or suspended gases separate from the liquid and naturally collect at various points in the system. Accumulations of gas may cause vapor lock that inhibits the effective distribution of the heated or cooled liquid, diminishing the efficiency of the heating or cooling system. Gas pockets may also induce noise and cause damaging cavitation in liquid distribution pumps. The introduction of gas into liquid distribution systems is therefore usually carefully controlled, but it cannot be completely avoided. Maintenance procedures, oxygen infiltration, and the injection of fresh liquid into the system all introduce some gas into the system.
Liquids that readily dissolve gasses at a temperature and pressure at which the liquids are injected into a system, and emit the gasses under operating temperatures and pressures in the system, are especially prone to the problems associated with gas accumulation. Such liquids include water, which readily absorbs oxygen and other gasses when cool, but emits the absorbed gases when heated. Because of its availability and heat transfer properties, water is commonly used in heating and cooling systems. Besides the undesirable affects of vapor locks, oxygen is a principal agent responsible for the corrosion of metal. Consequently, the removal of oxygen from heating and cooling systems is all the more desirable.
Gas removal from heating and cooling systems is well known. The gas is removed using venting devices referred to as de-aerators that are connected in various ways to the distribution pipes of the heating and cooling systems. The known de-aerators are generally expensive units that include a plurality of components encased in one or more metal housings connected to the distribution pipes. Inexpensive de-aerators are available, but they are generally much less effective at removing gas from the liquid.
An example of an expensive de-aerator is described in U.S. Pat. No. 5,490,874, entitled DE-AERATOR APPARATUS, which issued to Hans L. Kuster et al. on Feb. 13, 1996. The de-aerator includes a housing that forms an upright cylindrical chamber having fittings on opposite sides for the connection of the distribution pipes. The liquid flows through the distribution pipes into the chamber, and gas extracted from the liquid is exhausted through a valve controlled vent. The valve is opened and closed by the motion of a float that is buoyantly displaced by the rise and fall of the level of the liquid in the chamber. When the level of the liquid is below a certain point the valve is opened, permitting the accumulated gas to escape. When the liquid level is above the certain point the valve is closed, preventing the contents of the chamber from escaping. A concentrator that partially disrupts the flow of the liquid through the chamber extracts the gas bubbles and microbubbles from a liquid flowing through the chamber. The concentrator has a large surface area to volume ratio to facilitate the removal of gas from the liquid.
The less expensive de-aerators are typically adapted to be threadedly attached to a pipe fitting, such as a venting nozzle of a radiator, or other heating appliance. The less expensive de-aerators are constructed in a similar way with a float-based valve venting mechanism, but do not include a concentrator with a large surface area for removing gas from the liquid. The less expensive de-aerators are therefore adapted to remove large bubbles of gas from the liquid that rise under the force of buoyancy, but are inefficient at extracting finer bubbles and microbubbles from the liquid.
A disadvantage of all the known de-aerators is that they are expensive to construct and/or require special fittings that are time-consuming to install in a heating or cooling distribution system.
There therefore remains a need for a low-cost de-aerator that is easily installed without special fittings, and capable of efficiently extracting gas from a liquid conveyed through a distribution system.